1 How many desks do they buy every term?

题目

1 How many desks do they buy every term?
2 We must tie the young tree to the stick.
将句子变成被动语态,每空一词
3 You needn't do it now.It___ ___ ___ by you now.
4 People use metal for making machies.Metal___ ___ for making machies.
5.He made me do that for him .I___ ___ ____that for him.
6 Did they buld a birdge here a year ago?___a bridge __here by them a year ago?(把6第一句改为陈述句的时候,here 应该防在哪里,为什么)
还有,麻烦把每一句的答案后都做解释,我希望能够真正知道原因.

答案

1、How many desks are bought by them every term?这是一般现在时的被动语态：am、is、are + 过去分词（+ by sb.)2、The young tree must be tied to the stick by us.这是情态动词被动语态：情态动词+ be + 过去分...